For a radio communication system which wirelessly collects information in various places such as factories where various radio noises travel in all directions, it is desired to resist interference waves (radio wave noises with the same frequency band as radio signals for information transmission).
In the fields of mobile communication and indoor radio communication, the directivity of an array antenna is controlled to reduce the adverse effects of interference waves (see PTL 1 and 2). However, existing techniques for mobile communication and indoor radio communication generally require complicated processing, and it also takes time to control the antenna beam. Therefore, it is difficult to apply the techniques for mobile communication and indoor radio communication to a radio communication system used in a factory or the like.